The most prevalent sound is the ocean. The rising and falling roar of water breaking against rocks, cascading into white foam, and settling before a new swell raises it again. It is everywhere, present in everything. 

Below that is the breath of Sandrea. For you sit atop her now and can feel her breathing more than hear it, despite being covered with mud, vines, and various seeds that have determined the best method of propagation to be really sticky burr. It may not be immediately apparent, but for the great sauropod dinosaurs, particularly those with long necks, the act of breathing is a challenging engineering problem. Nature solved it with trial and error, but bioengineers, even at the height of Silicon Valley, did not have infinite budgets. So they had to reverse engineer their way to information nature had hidden from them in the distant past in order to get to a working prototype. The answer, as best they could guess, was air sacks, rather like a giant set of constantly working bellows that were always slowly pumping air rather than taking distinct breathes in and out because there wouldn't be time for that sort of dead space in a creature so large that had to move air so far. All of which is to say that the sound of Sandrea breathing is not a rhythmic in and out but instead a continuous thrum deeper but quieter than the pitch of the ocean, the two blending together in an uneasy harmony.

And then, all around you, are the lights. Well...not lights, lights are just the easiest metaphor for the abstraction of data concentrations. At this distance, it's not possible to meaningfully pick out individual signals (absent some very sustained duration interception coupled with multiple linked stations to triangulate individual signals). But clustering is visible, like the old pictures of cities taken from the night sky. You can see what used to be the city of San Francisco, its downtown wildly overgrown but nevertheless full of so many data devices in some form that it feels thick. And you can see a sense of the existing human settlement roving along the coast, full of people still communicating with one another and recording information. You can see a cluster of signals within the valley running from northeast of you to southeast of you, a mixture of what had once been the densest population area of the East Bay and the new settlements that have appeared there. And to the east, there are signs of the new migration moving into the area and a rough location of the marauder camp standing out as a signal spot where no ancient settlement was present due to a major regional land reserve for the Ohlone Indians. Roughly speaking, of course, since the mountains and valleys have shifted somewhat from the data you previously possessed. 

"hot damn" says Ailee, who had remained quiet for the climb, but has quietly added a little map marker in her drawing to note where your cat companion is, currently resting at the base of the neck below you. "Didn't want to break your flow, but damn, that was wild. I never thought I'd get to, like, be this close to Sandrea, or any of the colossi. I've only had cameras and stories to build up my info."